Georg Fischer Rotor-X™ 5931.511 P51530-P0 0.5"-4" Signet 515 Paddlewheel Flow Sensor, Polypropylene Black PVDF Titanium. Simple to install with time-honored reliable performance, Signet 515 Rotor-X™ Paddlewheel Flow Sensors are highly repeatable, rugged sensors that offer exceptional value with little or no maintenance. The Model 515 sensors are offered in a variety of materials for a wide range of pipe sizes and insertion configurations.